The invention relates to the condensation of a coolant of an automotive air conditioning system and in this connection concerns a process as defined in the introductory part of claim 1. Furthermore, it concerns a condenser as defined in the introductory part of claims 6 and 16. The condenser is intended in particular but not exclusively for carrying out the process. The features of the introductory parts of claims 1, 6 and 16 are known from the Patent Abstracts of Japan with publication number 03122472 A (date of publication: May. 24, 1991).
In connection with the known process and the known condenser, partial condensation takes place first on an upper vertical level of the condenser. A vertical distributing/collecting tube has in this connection at the same time the function of a gas separator. The path of flow of the interior coolant branches out into two parallel paths of flow. The first parallel path is fed in this connection from the upper zone of the gas separator that contains the separated gas phase, and feeds its coolant mixture consisting of saturated liquid and gas phase into a second gas separator, which is separately arranged on the outlet side. Said second gas separator communicates with a second path, in which the coolant is taken from the liquid charged in the first gas separator and supercooled. The supercooled liquid and the liquid taken from the second gas separator are subsequently united again and jointly withdrawn from the condenser. In connection with said known condenser, however, the level of the liquid in the first gas separator is variable depending on different and/or changing filling amounts of the interior coolant and/or changing operating conditions of the motor vehicle. Therefore, an unwanted admission of the liquid phase of the first gas separator, which is present only in the form of liquid, into the first parallel path can be only avoided with a very wide diameter of the first gas separator, which consequently is connected with very high filling amounts and high space requirements. This is contrary to the requirements with respect to minimization of the installation requirements in the motor vehicle, the ecologically desirable limited use of interior coolant that is harmful to the environment, as well as in regard to the generally desired lowest possible use of materials. On the outlet side, too, the known condenser comprises a great number of elements and line connections, which should be avoided to the greatest possible extent, and, furthermore, poses the additional risk of leakage.
The invention is based on the problem of achieving even with different and/or changing filling amounts of the interior coolant and/or changing operating conditions of the motor vehicle a safe condensation and supercooling function even with a small amount of interior coolant, while at the same time permitting the condenser to be designed in a compact form.
Said problem is solved by the process according to claim 1 and the condenser according to claim 6 or 16.
As opposed to the known condenser, according to the invention, the first and the second parallel paths of the first or second heat exchanger tube are practically fed with the same mixture of fluid and gaseous phase of the interior coolant as the latter exits in terms of flow from the last three heat exchange tubes. Any relative changes that might occur in the mixture are only minor in this connection and are caused, for example by differences in inertia, or due to the fact that the inlet into the first and second flow path takes place at different height. No provision is made for any device for dividing the liquid and the gaseous phases into the first and the second parallel path of flow. Instead, supercooling and thus also automatic resorption of any gas phase that might still be present is accomplished in that in the second path of flow, the interior coolant is exposed longer to the cooling effect of the external coolant than in the first path of flow. Claims 2 to 4 show various preferred possibilities in terms of process engineering for slowing down the rate of flow of the interior coolant along the second path of flow, which is required for such longer exposure, and claims 7 to 9 show various preferred possibilities for achieving this in terms of apparatus. It can be seen that provision is made alternatively for throttling down the flow of the coolant along the second path of flow and/or for a differential pressure level on the inlets of the first and the second paths of flow, whereby the different pressure levels at the inlet side can be produced by changing the rate of flow of the interior coolant based on the Bernoulli effect, thus through a nozzle characteristic. It is already known per se from the Japan Abstracts with publication number 10009713 A (date of publication: Jan. 16, 1998) to feed each path of two parallel pathsxe2x80x94said paths being both intended for supercoolingxe2x80x94separately, specifically by way of partial condensing, on the one hand, and only from the liquid phase of a gas separator that is interconnected following partial condensing, on the other hand. Therefore, in this case too, the one parallel path is supplied from admitted liquid phase.
Furthermore, it is not assured that the other parallel path will not carry along a gas phase from the condenser in spite of re-connecting with the first-mentioned parallel path. This construction, which has only become known very recently, therefore stems from the preconceived notion of prior art according to the introductory parts of claims 1, 6 and 16, which is that a path of supercooling has to fed with a liquid phase of a partially condensed coolant.
The procedure as defined by the invention and the invented condenser, like the aforementioned prior art, are based on the principle of dividing the path of flow after partial condensation of the interior coolant into two paths of flow, acting on the interior coolant in different ways.
In addition, a rather conventional process with associated condensers is available in which the interior coolant, following partial condensation, is directly passed on and put into a supercooled state without division into parallel paths of flow influencing the coolant in different ways, whereby, however, the supercooling zone is also in this case fed by liquid phase of the partial condensation carried out previously. In this connection, the usual procedure comprises connecting a gas separator upstream of the supercooling zone in the way as realized in the prior art with respect to the second path of flow (see in particular DE 42 38 853 A1 as well as Patent Abstracts of Japan J07180930 A2, published on Jul. 18, 1995, and J09166371 A2 published on Jun. 24, 1997).
According to the process according to claim 5 and a corresponding further development of the condenser according to claim 10, pre-condensation takes place in terms of location below the site for further influencing the interior coolant along the two aforementioned parallel paths of flow. Arranging pre-condensation tubes in the lower zone of a condenser is known per se (see, for example the aforementioned Patent Abstracts of Japan with file numbers J07166371A2 and J0387572 A2.
In furtherance of said idea of the present invention, said type of construction is used in order to obtain on the outlet side of the condenser the highest possible filling level range of a gas separator on the outlet side, and to be able to absorb there changes depending on different and/or changing filling amounts of the interior coolant and/or changing operating conditions of the motor vehicle without adversely affecting the function of the condenser. Due to the available great height it is possible in this connection to make do with a small diameter of said gas separator on the outlet side, which, as mentioned before, is not possible with the gas separator on the inlet side according to the publication Patent Abstracts of Japan with publication No. 03122472 A2. The small cross section of the gas separator provided on the outlet side according to the invention is particularly made possible on account of the fact that at the most half of the mass of the flow of the interior coolant, and preferably a smaller proportion is conducted via said gas separator.
Claims 11 to 13 relate to special constructional features of the last-mentioned type of design.
On the other hand, claim 14 with the further development according to claim 15 offers an alternative solution for the case in which pre-condensation, as with the object of the Patent Abstracts of Japan with publication No. 03122472 A2, on which the introductory parts of claims 1 and 6 are based, is carried out above the site of division of the path of flow of the interior coolant into two parallel paths of flow. As mentioned above, with said known condenser, provision is made for a separate gas separator located on the outlet side. The invention according to claims 14 and 15 integrates said gas separator in the center section of a distributing/collecting tube without the necessity of having to divide the distributing/collecting tube in the horizontal direction in a plurality of chambers. Dividing a distributing/collecting tube in several chambers disposed one on top of the other is known per se (see, for example, Patent Abstracts of Japan J09166371 A 2, where, however, none of the chambers is developed further into a gas separator.
Claim 16 relates to a further development and further enhancement of the invention described above. As far as technically possible, the full content of the features of said development and improvement is included also in the object of claim 16 and the further developments of the latter.
The further development and further enhancement of the invention according to claim 16 are also made use of in particular by the process claim 1 and preferably by the process claim 2 as well.
An additional, i.e. a fourth exemplified embodiment of the object of the invention is described in special detail, stating in particular an alternative to the basic structure of the first and second exemplified embodiments. The introductory part of claim 16 is based in this connection on claim 6 and particularly includes also the special arrangement and design of the collecting container realized in the first and second exemplified embodiments.
Also the claims 7 to 9 as well as 11 to 13 are included in this connection as claims 17 to 22, whereby the present fourth exemplified embodiment concretely contributes to the realization of claim 7, to which the claims 8 and 9 represent possible alternatives also within the framework of the present fourth exemplified embodiment.
Claim 23 with its further developments in the claims 24 to 27 specifically relates to the object of claim 13, which is included also in claim 22, and may also be protected independently in the present fourth exemplified embodiment as this is the case also especially in the first and second exemplified embodiments.
The coolant inlet 10 is arranged in the condenser at the bottom both in the first and second exemplified embodiments. The coolant then flows through the chambers 22, 24, 26 and 28 in the upward direction against the direction of gravity.
Especially in connection with lower rates of flow of the coolant, it may occur that liquid coolant and lubricating oil carried along by the coolant from the coolant circulation each may get separated in the lower chamber zones, which may more or less clog the lowermost xe2x80x9cthirdxe2x80x9d heat exchanger tube 14 entering in each case in the respective chamber, so that inner heat exchanging surface area is lost and the efficiency of the condenser is reduced. Furthermore, especially the oil that is separated in the lower zone of the chamber 24 is missing for lubricating the compressor of the coolant circuit.
The invention of the fourth exemplified embodiment is therefore based on the specific problem of enhancing the removal of oil from the condenser and preventing any blocking of individual xe2x80x9cthirdxe2x80x9d heat exchanger tubes designed in the form of flat tubes entering the lower chamber zone, thereby improving the efficiency of the condenser.
Said problem is solved in connection with a condenser with the features of the introductory part of claim 16 by the characterizing features of said claim.
With this condenser, the coolant enters the condenser at the top, and the superheating and condensation zone is connected from the top downwards in such a way that liquid coolant or oil no longer can get deposited in the lower chamber zones because a discharge takes place in each case from the lowermost tube into the next opposite chamber.
As compared to the first and second exemplified embodiments, furthermore, the intermediate channel 42 is utilized in a different way as well due to the changed vertical level at which the coolant enters into the distributing and collecting tube 6, namely for transporting saturated liquid upwards with gas bubbles against the direction of gravity into the upper zone of the collecting container 46, the function of which being otherwise basically the same as in the first and second exemplified embodiments of the main patent.
In contrast to the third exemplified embodiment, therefore, the functions of the present fourth exemplified embodiment according to claim 16 are comparable with the first and second exemplified embodiments.
The dryer insert is developed further in claims 3 to 27 especially with respect to the present fourth exemplified embodiment; however, it can be employed also in the first and second exemplified embodiments from which the present invention of further development ensues.